Conventionally, a coating agent composed of various kinds of polyorganosiloxane compositions have been coated on surfaces of products such as an ethylene-propylene-diene ternary copolymer (hereinafter, it is abbreviated to EPDM) rubber, thermoplastic olefinic elastomer (hereinafter, it is abbreviated to TPO) used for a weather strip for a vehicle to provide non-tackness, water repellacy, abrasion resistance, lubricity, and so on.
For example, a composition in which polyorganosiloxane having a hydrogen atom coupled to a silicon atom and/or organoalkoxysilane and curing catalyst are added to polydiorganosiloxane having a hydroxyl group at an end thereof is known as the coating agent. Besides, a composition in which polydiorganosiloxane is compounded to curing polyurethane is also known (for example, refer to Reference 1, Reference 2).
However, these coating compositions contain an organic solvent, and therefore, there are not only safety, sanitary problems and handling problems resulting from inflammability, but also a problem having a significant impact on a natural environment. Accordingly, a development of a water-based emulsion type coating agent which does not contain the organic solvent has been made. However, a coating film having durability, adhesiveness, and so on cannot be obtained by applying an organic solvent dilution type coating agent to a water-base as it is. Besides, there are problems in which a coating agent containing organoalkoxysilane is difficult to make it water-based because a silane component reacts with an isocyanate component and water, a coating film having good adhesiveness cannot be obtained.
On the other hand, an aqueous silicone composition in which various siloxane compounds are combined and compounded is proposed as an emulsion type silicon based coating agent (for example, refer to Reference 3). Besides, a coating agent in which chlorinated polyolefins having a maleic anhydride group, and spherical particles having elasticity are compounded to dehydrogenation condensation type silicone based emulsion is proposed to improve the adhesiveness and abrasion resistance of a coating film (for example, refer to Reference 4).
However, in the coating agent described in the Reference 3, there are problems in which the adhesiveness and the abrasion resistance of the coating film are not sufficient, and the coating film having sufficient adhesiveness and strength cannot be obtained relative to a solid-type rubber material and a material near thereto. Further, there are problems in which preservation stability of emulsion and a pot life (working life) after respective components are compounded is short.
The coating agent described in the Reference 4 is improved in coating uniformity, non-tackness, water repellancy, lubricity, adhesiveness with a base material, and so on. In addition, it is improved in prevention of occurrence of squeak caused by friction with a glass or the like under a state of being exposed to water, and prevention of a friction scratch to a metal paint surface. However, further improvement in abrasion resistance and environmental and safety improvements are required.
Further, a coating agent in which an amine-functional silicone emulsion and a polyurethane emulsion, and an epoxy resin or epoxy-functional silane are compounded is proposed as a coating agent having high abrasion resistance (for example, refer to Reference 5). Besides, a coating agent in which a silicone emulsion and a polyurethane emulsion are compounded with a predetermined ratio is also proposed (for example, refer to Reference 6).
However, there is a problem that the working life is short in the coating agent described in the Reference 5, and it is practically required to compound the organic solvent to obtain the sufficient working life. Besides, the abrasion resistance is not sufficient and the enough adhesiveness cannot be obtained for a base material composed of the EPDM and the TPO in the coating agent described in the Reference 6. Further, it is necessary to compound a super-high molecular weight polyethylene powder and ceramic beads to obtain performances such as low friction. In particular, it is very effective to improve the abrasion resistance to compound the super-high molecular weight polyethylene powder, but the powder in itself has a thermal softening point, and therefore, there is a problem in which characteristics thereof change largely depending on a thermosetting temperature and a heating time.